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Technical Dayta Sheet Compedium

CONTENTS
CONCRETE
REPAIR
CORROSION
CONTROL
GROUTS &
ANCHORS
PROTECTIVE
COATINGS
INDUSTRIAL
FLOORING
SURFACE
TREATMENTS
JOINT
SEALANTS
CONCRETE
JOINTING
ROOFING WATERSTOPS WATERPROOFING JOINT FILLERS
TIMBER
FLOORING
ALPHABETICAL
Fosroc® Renderoc LA55
Application Instructions
Preparation
The unrestrained surface area of the repair must be kept to a
minimum. The formwork should be rigid and tight to prevent
loss of material and have properly sealed faces to ensure
that no water is absorbed from the repair material. The
formwork should include drainage outlets for presoaking and,
if beneath a soffit, provision for air-venting. Provision must
also be made for suitable access points to pour or pump the
mixed micro-concrete into place.
Saw cut or cut back the extremities of the repair locations to
a depth of at least 25 mm to avoid feather-edging and to
provide a square edge. Break out the complete repair area to
a minimum depth of 50 mm up to the sawn edge.
Clean the surface and remove any dust, unsound or
contaminated material, plaster, oil, paint, grease, corrosion
deposits or algae. Where breaking out is not required,
roughen the surface and remove any laitance by light
scabbling or grit-blasting.
Oil and grease deposits should be removed by steam
cleaning, detergent scrubbing or the use of a proprietary
degreaser. The effectiveness of decontamination should then
be assessed by a pull-off test.
Expose fully any corroded steel in the repair area and
remove all loose scale and corrosion deposits. Steel should
be cleaned to a bright condition paying particular attention to
the back of exposed steel bars. Abrasive blasting is
recommended for this process.
Where corrosion has occurred due to the presence of
chlorides, the steel should be high-pressure washed with
clean water immediately after grit-blasting to remove
corrosion products from pits and imperfections within
its surface.
Reinforcing steel priming
Apply one full coat of Nitoprime Zincrich and allow to dry
before continuing. If any doubt exists about having achieved
an unbroken coating, a second application should be made
and, again, allowed to dry before continuing.
Substrate priming
Several hours prior to placing, the prepared concrete
substrates should be saturated by filling the prepared
formwork with clean water. Immediately prior to the
application of Renderoc LA55, this water should be removed
from the formwork.
Mixing
Care should be taken to ensure that Renderoc LA55 is
thoroughly mixed. A forced-action mixer is essential. Mixing
in a suitably sized drum using an appropriate spiral paddle
such the Protool HS2 140 x 600 M14 Helical mixing paddle
(product code: TT-614217) or equivalent at a slow speed
(400/500 rpm) using a heavy-duty mixer, 1500W such as
Protool MXP 1602 E (product code: TT-621941) or
equivalent is acceptable for the occasional one-bag mix.
Free-fall mixers must not be used. Mixing of part bags should
never be attempted.
It is essential that machine mixing capacity and labour
availability is adequate to enable the placing operation to be
carried out continuously. Measure 2.4 - 2.8 litres of drinking
quality water and pour three-quarters into the mixer. With the
machine in operation, add one full 20 kg bag of Renderoc
LA55 and mix for one minute before adding the rest of the
water. Mix for a further 2 - 3 minutes until a smooth even
consistency is obtained. Note that powder must always be
added to water. The quantities mixed may be scaled up as
required.
When the drill and paddle mixing method is used, the
complete 2.4 - 2.8 litres of water should be placed in the
mixing drum. With the paddle rotating, add one full 20 kg bag
of Renderoc LA55 and mix for 2 - 3 minutes until a smooth
even consistency is obtained.
It is recommended that the mixed product be passed through
a suitable coarse metal screen prior to placing or pumping to
highlight any unmixed material.
Mixing warning
As with other ‘one pack’ repair mortars, Renderoc LA55 may
exhibit satisfactory handling characteristics even though
inadequately mixed. This will result in a significantly lower
level of performance or possible failure. It is therefore
essential that mixing instructions are strictly adhered to with
particular emphasis on the quantity of water used and the
time of the mixing operation.
Placing
The mixed material should be placed within 30 minutes of
mixing in order to gain the full benefit of fluidity and of the
expansion process. If placing by pump, standard concrete
pumping practice should be followed. The pump and pipeline
must be ‘grouted’ with a rich cement slurry or mortar,
discharging the ‘grout’ as waste. Pumping should be
commenced immediately after ‘grouting’ in this way.
Renderoc LA55 when used for reinstatement of horizontal
areas, must be suitably restrained by formwork.
Low temperature working
In cold conditions down to 5°C, the use of warm mixing water
(up to 30°C) is advisable to accelerate strength development.
Normal precautions for winter working with cementitious
materials should then be adopted.
The material should not be applied when the substrate
and/or air temperature is 5°C and falling. At 5°C static
temperature or at 5°C and rising, the application
may proceed.
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